The fateful journey of 16 A-Grade polo ponies across Bass Strait remains a mystery as investigations begin into what happened before their owner found them “cold dead”.

The Australian Maritime Safety Authority, Department of Primary Industries, Parks, Water and Environment are investigating the incident, while the Wagga Equine Hospital conducts the autopsies.

Polo breeder and club owner Andrew Williams was transporting the ponies, normally stabled at the Willo Polo Club in New South Wales, from an event at the Barnbougle Polo Club in north-east Tasmania when he found 16 dead in the back of his truck on January 29.

An associate of Mr Williams, Paul Banks, told The New Daily Mr Williams knew “something was wrong” about 30 minutes after disembarking the Spirit of Tasmania in Port Melbourne.

Mr Williams had done the trip in the same truck and had loaded them on the “same boat” 11 times before, but called his “head groom”, who was transporting more horses, to see if his load was travelling well.

“My head groom said his horses couldn’t wait to get off his truck. I knew then that something was potentially wrong, as mine were not indicating the usual activity,” Mr Williams said in a statement.

When he reached his destination at a friend’s property in Yarra Glen, his greatest fears were realised.

Within an hour of leaving the boat, I had 16 horses that were cold dead and two fighting to survive.”

The two surviving ponies were offloaded at Yarra Glen, while the remaining 16 were sent to the Wagga Equine Hospital for necropsies.

When asked if the accident was “unprecedented”, Mr Banks said questions should be directed to the Spirit of Tasmania.

The Spirit of Tasmania was a sponsor of the Barnbougle Polo event, but has declined to comment due to the ongoing investigations.

“It was the same truck, the same boat and a warmer night, that’s why it’s all about the position and the airflow,” Mr Banks said. “It’s all about getting answers, that’s where we’re at.”

Mr Banks also said the horses didn’t die from food or bad water and “it would be sad if it happened again.”

“They’re 500-kilogram animals. It’s a question mark,” Mr Banks said.

RSPCA chief vet and chief executive officer Andrew Byrne told The New Daily it was a “tragedy” and the horses had endured horrible deaths.

Dr Byrne said he didn’t know what the truck looked like or if there was water on board, but could only surmise the owners would have noticed if the horses were sick while competing in the polo event.

“I doubt they were sick because they were competing,”Dr Byrne said, adding “sick horses are under more stress when they are transported,”

The New Daily has sought comment from the Department of Primary Industries, Parks, Water and Environment .